Integrated traction system for locomotives

ABSTRACT

The disclosure an integrated traction system for a locomotive. The system includes a primary electrical energy source, a traction load circuit, an auxiliary load circuit, a common DC link, s secondary electrical energy, and a controller. The electrical energy generated by the primary electrical energy source is shared between the traction load circuit and the auxiliary load circuit during a power mode through the common DC link. Further, the electrical energy form the secondary electrical energy source is supplied to the primary electrically energy source during cranking mode. The controller controls the switching of the integrated traction system between the two modes.

TECHNICAL FIELD

The present disclosure generally relates to an integrated traction system for a locomotive. More particularly, the present disclosure relates to a single alternator, to power each of traction loads and auxiliary loads of the integrated traction system.

BACKGROUND

A diesel-electric locomotive typically includes a diesel engine coupled to drive a traction alternator and an auxiliary alternator. The traction alternator is adapted to power one or more traction motors, which typically propel the locomotive. The auxiliary alternator is adapted to power auxiliary electrical equipment. Examples of the auxiliary electrical equipment may include, cooling fans, blowers, air conditioning units, traction alternator field excitation, battery charging, and light loads.

In conventional traction systems for locomotives, the auxiliary alternator consumes substantial space in the locomotive. Moreover, the auxiliary alternator requires a separate cooling circuit. This may cause an additional cost to the locomotive. Additionally, a boost converter is required, at the time of engine cranking, which may further add to the overall cost of the locomotive. Thus, it is desirable to provide a traction system, to drive the traction motors and the auxiliary equipment.

U.S. Pat. No. 7,256,513, describes a method for controlling a device connected to an auxiliary power bus of a locomotive. Although the method of the '513 patent may be effective for utilizing the energy from an auxiliary alternator, but is cost intensive and still requires space on the locomotive. In addition, should a failure event occur that causes a potential failure of the auxiliary alternators, power from the main alternator may not be available to run auxiliary electrical equipment.

The presently disclosed system is directed to overcome one or more of the problems set forth above.

SUMMARY OF THE INVENTION

The disclosure provides an integrated traction system for a locomotive. The integrated traction system includes a primary electrical energy source operable to provide electrical energy. Further, the integrated traction system includes a load circuit. The load circuit includes a traction load circuit and an auxiliary load circuit. The traction load circuit is adapted to propel the locomotive and the auxiliary load circuit is adapted to enable one or more auxiliary electrical functionalities associated with the locomotive. The load circuit also includes a plurality of electrical energy converters operable to convert electrical energy to electrical energy with a desired electrical characteristic. In addition, the integrated traction system includes a common Direct Current (DC) link. The common DC link is adapted to provide a common electrical connection between the primary electrical energy source and each of the traction load circuit and the auxiliary load circuit. Further, integrated traction system includes a secondary electrical energy source. The secondary electrical energy source is configured to feed electrical energy in the load circuit during a predefined event. Moreover, integrated traction system includes a controller. The controller is configured to control the integrated traction system to connect the primary electrical energy source to the common DC link during a power mode, and connect the secondary electrical energy source to the primary electrical energy source during a cranking mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary locomotive that illustrates an integrated traction system of the locomotive, in accordance with the concepts of the present disclosure;

FIG. 2 is a schematic of an embodiment of the integrated traction system of FIG. 1 illustrating an arrangement between various electrical components of the traction system, in accordance with the concepts of the present disclosure; and

FIG. 3 is a schematic of another embodiment of the traction system of FIG. 1 illustrating a Dynamic Brake grid and exciter battery in the traction system, in accordance with the concepts of the present disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a schematic of a general locomotive 10 including an integrated traction system 12. The locomotive 10 may be an electrically powered rail vehicle employing the integrated traction system 12 for propelling the locomotive 10. The integrated traction system 12 includes a plurality of mechanical and electrical components that cooperate to propel the locomotive 10. Any electrically powered vehicle or machine employing direct current (DC) traction motors for propulsion could incorporate the integrated traction system 12 with the disclosed embodiments.

The integrated traction system 12 includes a prime mover 14 and an alternator/generator set 16. The prime mover 14 may be an engine, for example, diesel engines, gas turbines, micro-turbines, sterling engines, fuel cells, spark ignition engines, or combinations of these. The prime mover 14 may utilize a variety of fuels such as diesel fuel, natural gas, gasoline or hydrogen. The alternator/generator set 16 may be an induction alternator, switch reluctance motor/generator, permanent magnet alternator, or any synchronous machine of which may receive power from the prime mover 14 by a mechanical shaft connection 18. Further, the alternator/generator set 16 is electrically connected to a set of AC traction motors 40 (FIG. 2) for propulsion. According to the exemplary embodiment illustrated in FIG. 1, the locomotive 10 may also include multiple pair of wheels 20, with each pair of wheels 20 rotatably coupled to the AC traction motors 40. In one embodiment, multiple traction motors 40 _(l) to 40 _(n) can be included in the locomotive 10. In one example, the number of AC traction motors 40 may depend on the size of locomotive consist. Furthermore, the integrated traction system 12 includes plurality of mechanical and electrical components detailed in FIG. 2.

Referring to FIG. 2, there is shown a schematic of an embodiment of the integrated traction system 12 of FIG. 1. The schematic illustrates an arrangement of plurality of mechanical and electrical components that cooperate to propel the locomotive 10. The integrated traction system 12 includes a primary electrical energy source 22. The primary electrical energy source 22 can be an alternator configured to generate electrical energy. The present embodiment shows primary electrical energy source 22, which may be an alternating current (AC) alternator/generator set 16. As referred to herein, the term “primary electrical energy source” refers to the AC alternator/generator set 16. The term “primary electrical energy source” and “AC alternator/generator set” may be used interchangeably throughout this disclosure. The primary electrical energy source 22 may include a permanent magnet exciter 24. The permanent magnet exciter 24 may include permanent magnet mounted on rotor core (not shown) in various pole configurations. Further, the rotor core is nested within a stator core (not shown) of a main generator 26. The main generator 26 may include the stator core and a stator winding (not shown). The stator windings may be wound on the stator core in various pole configurations. In operation, the permanent magnet exciter 24 may be rotated to produce a rotating magnetic field. The rotating magnetic field interfaces with the stator coils to induce AC current in the stator coils. The rotating magnetic field coils are excited through the main generator 26 field excitation chopper circuit. The combined effect generates an alternating current (AC) of a specific characteristic in the main generator 26. The characteristic of the AC is based on the pole configuration and position of the permanent magnet exciter and the stator winding.

Further, the main generator 26 may supply alternating current (AC) to a common direct current (DC) link 30 through a rectifier 32. In the current embodiment, the main generator 26 of the primary electrical energy source 22 is configured to provide a three-phase alternating current (AC) to the common DC link 30 through the rectifier 32.

The common DC link 30 may be said to include the rectifier 32. The three-phase AC from the the primary electrical energy source 22 is supplied to the rectifier 32. Thereafter, the three-phase AC is converted to direct current (DC) through the rectifier 32. In an illustrative example, the rectifier 32 may comprise an insulated gate bi-polar transistors (IGBTs). An IGBT is a three terminal power semiconductor device that combines the operational characteristics of fast switching of potentially large current. Other types of rectifier circuits such as diodes and other Silicone Controlled Rectifiers (SCRs) may be used for the rectifier 32. In one embodiment, the three phase AC from the primary electrical energy source 22 is received by the common DC link 30 and may be rectified and converted into DC by the rectifier 32 and further supplied to a load circuit 34.

The load circuit 34 includes a plurality of electrical loads. The load circuit 34 is primarily divided into a traction load circuit 36 and an auxiliary load circuit 38. The common DC link 30 functions as a common source of DC electrical energy for the traction load circuit 36 and the auxiliary load circuit 38.

The traction load circuit 36 may include a set of the AC traction motors 40. The AC traction motors 40 are coupled with the pair of wheels 20 of the locomotive 10. In an embodiment, a plurality of AC traction motors can be included in the traction load circuit 36. For example, there can be AC traction motor 40 _(l) to 40 _(n) propelling the locomotive 10.

The auxiliary load circuit 38, in an example, may include a plurality of auxiliary electrical devices, such as a radiator fan motor 42, a communication module 44, a heating, ventilating, and air conditioning (HVAC) motor driven air compressor 46, and other auxiliary electrical load 48. The auxiliary electrical devices are exemplary and may include any kind or type of electrical loads, including electrical lighting loads.

In another aspect of the disclosure a secondary electrical energy source 50, such as a storage battery is provided in the integrated traction system 12 and is electrically connected with the common DC link 30. In one embodiment, the secondary electrical energy source 50 may be an energy storage device such as a high Voltage (HV) battery pack, a bank of capacitors, or combinations of these. Since, the secondary electrical energy source 50 is connected to the common DC link 30. The secondary electrical energy source 50 may be configured to feed electric energy to the load circuit 34 during a predefined event. For example, in the event when the energy from the primary electrical energy source 22 is not sufficient to meet the energy need of the load circuit 34, the secondary electrical energy source 50 feeds electrical energy at such predefine event.

The secondary electrical energy source 50 and the auxiliary loads 42, 44, 46, and 48 are connected to the common DC link 30. By way of example, the AC traction motors 40, the auxiliary loads 42, 44, 46, and 48, and the secondary electrical energy source 50 may be connected to the common DC link 30 via respective electrical energy convertors 52.

In one aspect, the AC traction motors 40 may operate a voltage range of 600-700 V, whereas the radiator fan motor 42 can operate at a range of 60-75 V. Accordingly, if the voltage level of the common DC link 30, for powering both the traction load circuit 36 and the auxiliary load circuit 38 is set to a voltage level appropriate for powering the AC traction motors 40, the auxiliary equipment may not be able to be directly connected to the common DC link 30 because the voltage is different from the voltage required to power the auxiliary equipment. Hence each of the auxiliary load and the AC traction motors 40 may be individually connected to the common DC link 30 via the electrical energy convertors 52 operable to convert electrical energy to electrical energy with a desired electrical characteristic. The auxiliary load circuit 38 and the traction load circuit 36 may be individually connected to the common dc link 30 via a respective DC-AC or DC-DC converters 52, such as pulse width modulators (PWMs). The electrical energy convertors 52 are configured to convert the DC power, made available on the common DC link 30 by the rectifier 32, by converting AC power generated by the primary electrical energy source 22. In one embodiment, the electrical energy convertors 52 may be for example inverters, chopper circuits, buck, boost or buck/boost circuits, rectifiers or DC to DC convertors.

The electrical energy convertors 52 are depicted as a single module in FIG. 2, however each electrical load may have individual converter, such as convertors 52 a, 52 b, 52 c, 52 d, and 52 e. Similarly, the secondary electrical energy source 50 could be connected through a DC/DC converter 52 f. However, in practice such components are typically provided in the form of a convertor/inverter circuit and a separate convertor/inverter controller circuit. The electrical energy convertors 52 may be capable of selectively adjusting the frequency and/or pulse-width of their respective output to the AC traction motors 40 and auxiliary loads 42, 46, 44, and 48. Such adjustments enable each of the loads to operate independently. It is noted that the electrical energy convertors 52 are capable of bi-directional power flow and thus may be operated to perform both AC to DC conversion and DC to AC conversion functions. Thus, the same type of a circuit may be used to carry out both rectifier functionality and inverter functionality as discussed herein. For example, the DC/DC convertor 52 f may adjust the DC from the common DC link 30 to charge the battery (secondary electrical energy source 50), and also adjust the DC output from the battery to supplement electrical energy to the common DC link 30.

Further, the integrated traction system 12 includes a controller 54. The controller 54 is configured to control operating modes of the integrated traction system 12. In an example, the controller 54 may include a command module (not shown), and a sensory module (not shown) to perform various control related operations of the integrated traction system 12. The controller 54 may also include software which will issue commands to control operational functions, such as and not limited to operating switching devices 56 a and 56 b of the common DC link 30, of the integrated traction system 12. In an example, the switching devices 56 a and 56 b can be three pole switch or a bus bar.

In operation, the controller 54 may determine an operating mode for the integrated traction system 12. For example, the sensory module of the controller 54 may be configured to monitor a condition, such a drawn current in the auxiliary load circuit 38 of the integrated traction system 12 to determine the operating mode.

In one embodiment controller 54 may decide that the integrated traction system 12 may be operable in a power mode. The power mode refers to the operating mode when the electrical power from the primary electrical energy source 22 is consumed to power the AC traction motors 40 of the traction load circuit 36 and the auxiliary load circuit 38 via the common DC link 30. For example, the HVAC compressor 46 may consume electrical energy to condition the cabin air when powered via the common DC link 30. To enable the power mode, the controller 54 controls the switching devices 56 a and 56 b to connect the primary electrical energy source 22 to the traction load circuit 36 and the auxiliary load circuit 38 via the common DC link 30. In other words, the controller 54 closes the switching devices 56 a and 56 b.

In another embodiment, the integrated traction system 12 is operable in cranking mode. The cranking mode refers to an operating mode when the primary electrical energy source 22 exits power generation, and is set to operate as a power consumption device. In one example, the primary electrical energy source 22 may stop producing electrical energy and is adjusted to consume electrical energy for mechanical rotation. The mechanical rotation is primarily consumed to rotate and crank the prime mover 14 coupled through the mechanical shaft connection 18. In the cranking mode, electrical power is provided to the primary electrical energy source 22 from the secondary electrical energy source 50 that is the battery, through the respective DC/DC convertor 52 f. The cranking mode is enabled by the controller 54 by flipping the switching device 56 a and closing the switching device 56 b, such that the secondary electrical energy source 50 is connected to the primary electrical energy source 22 of the integrated traction system 12. The cranking mode is further described in conjunction with FIG. 3.

FIG. 3 illustrates another embodiment of the schematic of the integrated traction system 12. FIG. 3 illustrates a Dynamic Brake (DB) grid 58 in the integrated traction system 12. The DB grid is electrically connected to the common DC link 30 to feed electrical energy to the traction load circuit 36 and the auxiliary load circuit 38 through the common DC link 30.

Generally, electrically powered rail vehicles such as the locomotive 10 includes the traction load circuit 36 that selectively activates the AC traction motors 40 during propelling. However, when the locomotive 10 is retarding or during deceleration, the power from the prime mover 14 is reduced. In addition, the locomotive 10 also include conventional friction brakes and other mechanisms such as regenerative breaking mechanism for retarding or to decelerate and/or stop the locomotive 10. As the locomotive 10 decelerates, the momentum of the locomotive 10 is transferred to the AC traction motors 40 via rotation of the pair of wheels 20. The AC traction motors 40 acts as a generator to convert the kinetic energy of the pair of wheels 20 to electrical energy. This electrical energy is supplied to an electric grid and usually dissipated as heat via an array of resistors of the DB grid 58. However, to increase the efficiency of the locomotive 10, this electrical energy may be stored for later use or is partially used to power the auxiliary loads in the auxiliary circuit 38 such as 42, 46, 44, and 48. Examples of the auxiliary load may include a radiator fan, a blower motor, a motor driven compressor, an electric light system, blowers for cooling retarding grids, and the like.

In one example, during retarding, AC traction motors act a generator and generate electrical energy. The electrical energy generated in the AC traction motors 40 is supplied to the DB grid 58 and is be stored in the secondary electrical energy source 50 for later use or partly used to power the auxiliary load circuit 38. It should be noted that since the DB grid 58 is connected to the common DC link 30, the electrical energy generated at the DB grid 58 can be stored and used. This enables increased efficiency of the locomotive 10 and reduces fuel consumption. Further, the generated electrical energy at DB grid 58 can also power the auxiliary load circuit 38. Thus, when the engine is de-rated during retardation, electrical energy can still be generated to feed the auxiliary load circuit 38 because the common DC link 30 provides a common electrical link or connection with the DB grid 58.

In one embodiment, during the power mode, the electrical energy from the DB grid 58 can supply additional electrical energy to the common DC link 30 to charge the secondary electrical energy sources 50 (battery) or assist in providing electrical energy to the auxiliary load circuit 38. Whereas, during the cranking mode, when the primary electrical energy source 22 is not providing electrical energy, the controller 54 may control the switching devices 56 a and 56 b to connect the secondary electrical energy source 50 or battery to the primary electrical energy source 22. And, sufficient electrical energy from the secondary electrical energy source 50 may be diverted to the primary electrical energy source 22. The electrical energy from the battery may cause the mechanical rotation and crank the prime mover 14 coupled through the mechanical shaft connection 18.

Energy is required to rotate the engine to start the combustion in the prime mover 14. In the cranking mode, the battery is connected directly to the primary electrical energy source 22. The electrical energy stored in the secondary electrical energy source 50 (battery) and from the DB grid 58, through a convertor 52 g and a field chopper circuit 52 h provides electrical energy to the permanent magnet exciter 24 and the stator winding of the main generator 26, which turn the main generator 26 to act as a motor and thereby cranks the prime mover 14.

INDUSTRIAL APPLICABILITY

The locomotive 10 may be an electrically powered rail vehicle employing an integrated traction system 12 for propelling the locomotive 10. In operation, electrical energy is generated by powering the primary electrical energy source 22 via the prime mover 14. This electrical energy is fed into the common DC link 30, which acts as common electrical power source for the traction load circuit 36 and the auxiliary load circuit 38. The traction load circuit 36 powers the AC traction motors 40 to propel the locomotive 10. The auxiliary load circuit 38 includes a plurality of electrical loads, which also consume electrical energy off the common DC link 30. Hence, all the electrical energy provided by the primary electrical energy source 22 is converted into DC electrical energy through the common DC link 30 and is supplied both to the traction load circuit 36 and the auxiliary load circuit 38. In such arrangement, the common DC link 30 acts as a common energy source for the traction load circuit 36 and the auxiliary load circuit 38.

The common DC link 30 eliminates need for separate electrical power source say an alternator for the auxiliary load circuit 38. Also, the primary electrical energy source 22 may be sized and rated for the maximum power needed to be supplied to respective components in the traction load circuit 36 and the auxiliary load circuit 38, considering the available electrical energy available from the secondary electrical energy source 50 and the DB grid 58. Hence, the primary electrical energy source 22 may take up less space than the space required to house the individual alternators and may require less maintenance and may be less expensive than providing separate electrical energy source for the individual circuit.

It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, one skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim. 

What is claimed is:
 1. An integrated traction system for a locomotive, comprising: a primary electrical energy source operable to provide electrical energy; a load circuit, including: a traction load circuit adapted to propel the locomotive; an auxiliary load circuit adapted to enable one or more auxiliary electrical functionalities associated with the locomotive; a plurality of electrical energy converters operable to convert electrical energy to electrical energy with a desired electrical characteristic; a common Direct Current (DC) link adapted to provide a common electrical connection between the primary electrical energy source and each of the traction load circuit and the auxiliary load circuit; a secondary electrical energy source configured to feed electrical energy in the load circuit during a predefined event; and a controller configured to control the integrated traction system to connect the primary electrical energy source to the common DC link during a power mode, and connect the secondary electrical energy source to the primary electrical energy source during a cranking mode. 